The present invention is related generally to Infrared Communications Controllers (IrCC) for use with devices, such as, for example, personal computers, more particularly to an IrCC consumer IR (TV remote) for general-purpose programmable Amplitude Shift Keyed serial communications interface that includes a carrier frequency divider, a programmable receive carrier divider, a range sensitivity register and receive demodulator and transmit modulator and, most particularly, to a Consumer Infrared Communications receiver carrier frequency range detection circuit and method.
An IrCC typically comprises two main architectural units, a uniform asynchronous receiver/transmitter (UART) and a synchronous communications engine (SCE). Each unit is supported by its own unique register set.
In infrared communications controllers utilized with personal computers, the IrCC is usually incorporated into a semiconductor chip. When designing a semiconductor chip, there is considerable competition between the available resources or space on the chip and the ever increasing functions required to be accomplished by the applications with the limited physical size of the chip. Specifically, only recently on a chip of silicon roughly an inch square, Intel.RTM.'s Pentium.RTM. chip held about three (3) million transistors, or tiny electronic switches. More recently, the number of transistors on the same inch square chip has been increased to between five (5) and six (6) million. Thus, while the number of transistors or electronic switches that can be implemented on a chip have increased, so has the number of functions that auxiliary chips, which communicate with the CPU are required to perform. Given this constant need for increased functions, chip designers are constantly looking for ways to decrease the amount of space, i.e., the number of electronic switches in a chip required to do a specific function.
Over the past fifteen (15) years, the tools required to manage growing communication needs have expanded. Unfortunately, the physical act of communicating hasn't always been simplified. An example of the complexity of communicating involves the transfer of data from a notebook computer to a laser printer. This seemingly simple task requires that the mobile PC be connected by a cable to a printer. Alternatively, the data contained on the notebook computer could be saved to a diskette and then inserted into a desktop computer, the data being accessed by an application on the desktop and then the data is printed on the printer. Either of these procedures is generally time consuming.
Recently, personal computer (PC) manufacturers or PC developers have produced personal computers having ports for communicating data to and from input/output devices via wireless infrared signals. Infrared radiation is very directional and generally is most effective when the infrared transmitting device is aligned within fifteen (15.degree.) degrees left or right of the receiving IR port.
The infrared transmitting device encodes data and sends it via infrared signal to the receiving device, where it is decoded, operating much the same as a modem without wires. By using the software for infrared use, the system notifies the user when it "sees" another IrDA-equipped device. Once another infrared-equipped device is "found," the files to transmit are selected and the process initiated. The line of sight must be unobstructed between the transmitting device and the receiving device, since infrared radiation will not pass through or around people or things.
Recently, IBM.RTM. included an infrared communications port in the Think Pad.RTM. notebook computer to facilitate point-to-point communications with other Think Pad.RTM. computers or systems equipped with an infrared port. The IR port is located on the rear or side of the computer. Each of the IR data ports supports the new IrDA (infrared data association) standard which enables short-range, point-to-point wireless interconnection of computers and peripherals without cabling. The adapters created visible links between computers and computer peripherals equipped with similar technology. Instead of physical attachment by means of cables attached to a computer's serial or parallel port, these infrared ports make a quick and easy connection through the use of infrared radiation.
In TV remote infrared control, IR signals are typically transmitted from the remote control to the TV, VCR or stereo and software converts the signals from the encoders in the remote control into digital instructions to change channels, raise or lower the sound volume, etc. This requires that the transceivers be incorporated in both the remote control and the TV, VCR, or stereo. Recently, personal computer designers have moved toward incorporating more infrared communication functions into the PC including the Consumer IR (TV Remote) control function. With many infrared communication functions being incorporated into PCs, the use of wireless infrared communications has become more important.
Once the decision was made to include the Consumer IR (TV Remote) function in a PC, it became necessary to determine effective means for tuning the receive portion of the PC receiver for tolerances around the absolute frequency transmitted from the transceiver for a wide range of programmable frequencies. This discrimination or frequency checking function should be accomplished in a way that conserves chip space while providing for the rapid and accurate establishments of IR communications between the PC and the remote IR communications device.
Thus, there is a need for a Consumer IR TV remote function in an Infrared Communications Controller of a personal computer that effectively tunes in the IR receiver for each tolerance around the absolute frequency that is being sent from the other transceiver. Such a Consumer IR TV remote function should include a carrier frequency range detection circuit that performs the receiver/discriminator function within the Consumer IR portion of the Infrared Communications Controller. This receiver/discriminator function should require as little chip space as possible while rapidly and effectively establishing IR communications with the remote IR communications device.